Apparatus for washing trays conventionally includes a conveyor on which the trays are horizontally supported. For example, see U.S. Pat. No. 3,939,854. Recent developments in connection with hospital food trays have resulted in insulated trays having a thickness of between 2 and 41/2 inches thick. Such trays have deep pockets which are not adequately cleaned by conventional washing apparatus. See U.S. Pat. No. 3,799,386. The present invention recognizes the deficiencies of the prior washers and is directed to a novel structural interrelationship for satisfactory washing insulated trays in a reliable manner.